See where I'm going with this
Glimpse, the Unthinkable's second ability prevents it from being chosen for spells and abilities that specifically ask a player to "choose" or make a "choice" among creatures or other permanents, such as found on cards like Call to the Void, Divine Reckoning, and Vesuvan Shapeshifter
Which means most people exile 7 cards and pay only a single blue to draw 3 cards
Moggcatcher is in similar shape, appearing only in Nemesis and as part of The List, and sitting at roughly $11 in its cheapest form
The reason for that was that Rith, the Awakener came along at the most favorable time in history for a good, large finisher in its colors thanks to the rise of Fires of Yavimaya
You drop one of three creature types into play attacking alongside her